A. Field of the Invention
The present invention relates to improvements in sensitive edges employed on doors or similar devices in transit vehicles.
B. Description of the Prior Art
Increased emphasis on safety for transit vehicles has imposed stringent requirements on door systems, lifts, high/low platforms and transit car treadles and particularly in the area of the sensitive edges employed on these devices to sense passengers or objects trapped or engaged by the doors, lifts, and treadles. The most direct means of sensing objects is through the use of sensitive door edges, but historically sensitive edges have been complex in design and somewhat critical in application requiring a high rate of repair along with high maintenance requirements.
Three prior art types of sensitive edges are mechanical such as the type illustrated in U.S. Pat. No. 2,476,111; electrical as illustrated in U.S. Pat. No. 2,493,157 and pneumatic as illustrated in U.S. Pat. No. 3,303,303. These prior art systems, however, are often sensitive to temperature variation, debris carried by the environment and wear over long periods of use thereby reducing their utility.